Neil Patrick Harris, ‘How I Met Your Mother’

Supporting actor, the un-usual suspects

Neil Patrick Harris is perfectly happy keeping his snappily dressed rascal Barney on the CBS sitcom “How I Met Your Mother” in the growth-free zone for the time being.

“We’re only in our sophomore year coming up, so things don’t need to get resolved too quickly in our world,” says Harris, who proudly calls his character “Mr. Jesterhead” and relishes not having to carry the show’s weight. “The rest of the gang work very hard to make it realistic and heartfelt, and my job is to make the audiences on couches laugh.”

Harris sees the pranksterish, womanizing, cheerily insult-laden Barney as following in the hallowed footsteps of sitcom sidekickery that includes Larry from “Three’s Company,” Kramer on “Seinfeld” and “Taxi’s” Reverend Jim. He knew the challenges, though.

“What Barney does on paper is not really friendlike,” says Harris, 32. “So there has to be an element of I’ve-got-your-back, even though he’s often setting his friends up and then laughing in their face. I try to inject likability in there, in some strange form.”

And because Harris hopes to play Barney for a long time, he’s become protectively particular about the character’s threads.

“I didn’t want period-specific suits,” he says. “If you’re lucky enough to have a show that lasts long enough to be syndicated, it’ll be on a decade later, and I didn’t want (the equivalent of) those Cosby sweaters. So I wanted him to be very Rat Pack: thin tie, thin-cut, hipster Sinatra.”

On the subject of career longevity, the New Mexico-born Harris takes comfort in words Steven Bochco told him and his parents before the teen-doctor series “Doogie Howser, M.D.” kicked off Harris’ career at the impressionable age of 16.

“He said, ‘You’ll ride this wave of success, but it will inevitably crash and wash ashore. But know that waves come in sets, and you may have to sit on your board a long time between sets.'”

The advice empowered Harris to keep at bay the desire to maintain hot status, a celebrity side effect he feels destroys a lot of younger actors.

“Fame is not unlike VIP clubs in L.A. bars: You can’t get into certain doors all the time,” he says. “If you just keep trying for that, you’re going to burn yourself out.”

It’s meant that over the years since “Doogie” ended in 1992, he’s taken jobs in everything from the spiders-in-space feature “Starship Troopers” to made-for-TV movies to acclaimed stage plays.

Reflects Harris, “It allows time to go by between a Doogie Howser and a Barney Stinson.”

SOUND BITES

Favorite scene of last season?

“The flashback that showed how he became Barney, that the woman he loved broke his heart. I sang a song into the camera and I was weeping. That was really fun to do.”

What shows do you watch?

“Project Runway,” “Top Chef,” “The Amazing Race”

Underrated actor?

“Bradley Whitford. His work on ‘The West Wing’ was extraordinary. He was able to say pages and pages and pages of dialogue casually, comfortably, and with great charm and wit.”